A new study by PhilaU associate professor Jeff Ashley found PCBs in supplements and vitamins for children, 6ABC reported April 9. The supplements contain fish oil, which promotes brain development, but the fish oil often contains PCBs, a toxic chemical banned in the 1970s but still lingering in the environment. Ashley advised parents to look for supplements made from smaller fish, which accumulate lower levels of PCBs, and also to feed their children fresh fish, which tend to have lower levels of PCBs than the supplements.